China expands Beidou Navigation System with dual Satellite Launch

September 18, 2012

China has successfully launched two Beidou-2 Navigation Satellites to their desired transfer orbits to expand its Beidou Navigation System that will provide regional coverage for China and neighboring countries by the end of this year, according to Chinese officials. A Long March 3B Launch Vehicle lifted off from the Xichang Satellite Launch Center at 19:10 UTC on Tuesday, September 18, 2012 carrying the Compass M5 and M6 Satellites to their targeted transfer orbit with both satellites entering service once achieving a circular orbit of 12 hours at an inclination of 55 degrees. According to Chinese Sources, the Flight was nominal. The CZ-3B is 54.8 meters long and has a main diameter of 3.35 meters weighing 458,970 Kilograms when flying in its enhanced version that features larger propellant tanks and improved navigation systems. After Liftoff, the Long March 3B Launcher which is the largest of the Long March Rocket Family, was powered by its core stage and four liquid strap-on Boosters which all use 37,700 Kilograms of Unsymmetrical Dimethylhydrazine and Nitrogen Tetroxide as propellants. Each of the Boosters is 15.3 meters long and 2.25 meters in diameter. The strap-ons provide 740 Kilonewtons of thrust with their YF-25 engine and are jettisoned after burnout and fall back to Earth. For this mission, the drop-zone was located in the Guangxi Province. The drop-zone for the first stage was also located in Guangxi and teams were present to recover any large debris. The Core Stage of the vehicle features four YF-20C engines that provide a combined thrust of 2,962 Kilonewtons. The stage is 23.3 meters in length and holds 171,800 Kilograms of storable propellants at blastoff. After Stage 1 Burnout, the second stage continued powered flight. It also uses Hydrazine and NTO as propellants on its way uphill. The second stage features a YF-22E Main Engine providing a thrust of 742 Kilonewtons as well as four 12kN Vernier Engines. The stage is 10 meters in length consuming 49,0=0 Kilograms of propellants during flight. When its job was done, it separated from the vehicle and the cryogenic third stage started its burn.

*File Image* Photo: www.ChinaNews.com

The upper stage of the Long March 3B is powered by two YF-75 Engines - each providing 79 Kilonewtons of Thrust. Third Stage propellants are 18,200 Kilograms of liquid Oxygen and liquid Hydrogen. The Upper Stage has a reduced diameter of three meters and is 12.4 meters long. For this dual-payload launch, vehicle had been outfitted with a larger, 3.7-meter diameter Payload Fairing, 10.7 meters in length, to accommodate the two spacecraft. Using a special adapter, the satellites were launched in a stacked configuration. Once in its desired orbit, the launcher deployed the first satellite and jettisoned the adapter before releasing the second payload. Both satellites were released into elliptical orbits with an altitude of ~21,528 Kilometers and an inclination of 55 Degrees. CZ-3B/E has a Low Earth Orbit Payload Capability of 12,000 Kilograms; it can carry 5,500 kilograms into Geostationary Transfer Orbit.

The M5 and M6 Compass satellites are now set to enter the Beidou Navigation and Communication Constellation that is being established by China. The Beidou-2 Constellation of Satellites is currently under development and will feature 35 orbiting satellites once complete. At the end of 2012, China plans to provide regional Beidou Navigation services covering China and neighboring regions. By 2020, the System is expected to provide global navigation capabilities. Beidou provides free service to civilian users as well as licensed service for the Chinese Government. The free service is limited in accuracy with a navigation accuracy of 10 meters and 0.2m/s in velocity and a timing accuracy of 10 nanoseconds while the military service will provide a much higher accuracy. The complete constellation of Satellites will feature five Spacecraft in Geostationary Orbit and 27 Satellites in a Medium-Earth-Orbit as well as three Compass Satellites in inclined geostationary orbits. Compass M5 and M6 are based on the DFH-3 Platform and feature two deployable solar arrays for power supply and a Propulsion System for orbital maneuvers in addition to the satellite payload. The Satellite body consists of a hexahedral structure being about 2.2 by 2.0 by 3.0 meters in size with a liftoff weight of 3,800 Kilograms and a payload mass of up to 450 Kilograms that is supported by the satellite bus. Both of the satellites are now starting a period of on-orbit commissioning during which they will use their Propulsion System to maneuver to their respective operational orbits.

The most recent dual Compass Launch took place from Xichang in April of 2012.This launch was the 167th successful orbital launch by China, the 167th launch of a Long March Rocket and the 12th successful launch of the year for China. It was the 75th launch from Xichang and the 7th successful Xichang launch of the year.The next Chinese Launch is likely taking place later this month when a Long March 2D Rocket will loft the Venezuelan VRSSS-1 Remote Sensing Satellite to Orbit. The next Compass launch is planned for October via CZ-3C.

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